Abstract
We investigate the general features of thermal emission and absorption of radiation in photonic crystals. The light-matter interaction is strongly affected by the presence of the three-dimensional photonic crystal and the alteration of the photonic density of states can be used to suppress or enhance the thermal emissivity and absorptivity of the dielectric structure. Our analysis shows that the thermal response of the system depends on both the elementary absorbers/emitters and the photonic reservoir characteristics. In particular, we demonstrate that, depending on the system configuration, the thermal emission may exceed the free-space radiative energy density given by Planck's law. This modification of the Planck's law is achieved without altering the optical properties of the absorber/emitter medium, which remain consistent with the usual definition of a frequency and angle dependent grey-body. We also evaluate the rate of spontaneous emission, stimulated emission and absorption for thermally driven two-level atomic systems in a photonic crystal, and introduce effective A and B coefficients for the case of a photonic crystal. © 2005 OSA/FIO.